Primary switched-mode power supply unit

Abstract

A primary switched-mode power supply unit having an auxiliary power supply for a control unit controlling a primary power circuit breaker connected in series with a first primary winding and a primary voltage regular connected to the control unit. The auxiliary power supply has a secondary primary winding across which a series circuit of a diode and a capacitor is connected. A current limiting circuit breaker is connected between the auxiliary voltage input of the control unit and a ground, the actuating input of said current limiting circuit breaker being connected to an output of an overcurrent controller.

What is claimed as new and desired to be secured by Letters Patent of the United States is: 
     
       1. A primary switched-mode power supply unit, comprising: an auxiliary supply providing operating voltage to an auxiliary voltage input of a control unit which controls a power circuit breaker connected in series with a first primary winding;   a primary voltage regulator having an output providing an overvoltage control signal to the control unit, said auxiliary supply having a secondary primary winding across which a series circuit of a diode and a capacitor is connected;   a primary current controller having an output providing an overcurrent control signal to the control unit; and   a current-limiting circuit breaker connected between said auxiliary voltage input of the control unit and a ground, the closing of said current-limiting circuit breaker being responsive to said output of said primary current controller and the opening of said current-limiting circuit breaker being responsive to said operating voltage reaching a predetermined threshold;   wherein the current-limiting circuit breaker includes a pnp transistor and an npn transistor, each having a collector connected by a respective collector resistance of the other transistor, and a base-to-emitter resistance connected between each transistor's base to its emitter;   wherein the auxiliary voltage input of the control unit is connected to the emitter of the pnp transistor, and the emitter of the npn transistor is connected to the ground; and   wherein the collector of the npn transistor comprises an actuating input for closing the current-limiting circuit breaker.   
     
     
       2. A primary switched-mode power supply unit according to claim 1, wherein outputs of the said primary voltage regulator and the primary current controller are connected to a clock input of the control unit. 
     
     
       3. A primary switched-mode power supply unit according to claim 1, wherein the outputs of said primary voltage regulator and said primary current controller are connected to each other by a decoupling diode. 
     
     
       4. A primary switched-mode power supply unit according to claim 1, wherein said primary voltage regulator and said primary current controller each comprise an opto-isolator. 
     
     
       5. A primary switched-mode power supply unit, comprising: a power circuit breaker coupled in series with a first primary winding;   a control unit for controlling said power circuit breaker;   an auxiliary power supply for supplying operating voltage to said control unit, said auxiliary power supply comprising a second primary winding across which a series circuit of a diode and a capacitor is coupled;   a primary voltage regulator having an output coupled to provide an overvoltage control signal to said control unit;   a primary current controller having an output coupled to provide an overcurrent control signal to said control unit; and   a current-limiting circuit breaker coupled across said auxiliary power supply and having a trip input coupled to the output of said primary current controller for controlling its closing, its opening being controlled by the operating voltage of said auxiliary power supply reaching a predetermined threshold level.   
     
     
       6. A primary switched mode power supply unit according to claim 5, wherein the current-limiting circuit breaker includes a pnp transistor and an npn transistor, each having a collector connected by a respective collector resistance of the other transistor, and a base-to-emitter resistance connected between each transistor's base to its emitter. 
     
     
       7. A primary switched mode power supply unit according to claim 6, wherein said operating voltage is applied to an auxiliary voltage input of the control unit, said auxiliary voltage input being connected to the emitter of the pnp transistor, and the emitter of the npn transistor being connected to a ground of said auxiliary power supply. 
     
     
       8. A primary switched mode power supply unit according to claim 6, wherein the collector of the npn transistor comprises the trip input of the current-limiting circuit breaker.